1) Field of the Invention
This invention relates generally to fabrication of semiconductor devices, and to the fabrication of metal layers comprised of alpha phase Tantalum (Ta) and more particularly to Ta layers comprised of alpha and beta phase tantalum.
2) Description of the Prior Art
As ultra-large scale integrated (ULSI) devices extend into deep submicron generations, new interconnect schemes and materials are essential to drive performance and reliability. Owing to its lower bulk electrical resistivity (1.7-2.2 micro-ohm-cm) and higher electromigration resistance, copper has begun to displace aluminum as the interconnect material of choice. Nonetheless, copper is a fast migrating species in silicon based devices, and its inherent chemical reactivity renders it susceptible to oxidation and corrosion. Hence, encapsulation of the copper is essential, and a conductive barrier should be a suitable encapsulant that can act both as an effective barrier to copper diffusion and an adhesion promoter to the surrounding dielectrics while maintaining the overall performance. Tantalum and its related compounds such as tantalum nitride and tantalum silicon nitride have attracted much attention to their role as copper diffusion barriers. Being a refractory metal, tantalum is also relatively immiscible with copper, and is thus an excellent barrier material for ULSI applications. However, better methods and structures for forming interconnects with Ta barrier layer are needed.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering U.S. Pat. No. 6,339,258b1 (Cooney, III et al.) shows a tantalum layer.
U.S. Pat. No. 6,221,757b1 (Schmidbauer et al.) shows a method of making microelectronic structures using a tantalum.
U.S. Pat. No. 6,297,140b1 (Uzoh et al.) shows a method for a Cu stud that involves a barrier layer.
U.S. Pat. No. 6,291,885b1 (Cabral, Jr. et al.) discusses a multi-layer of TaN and Ta as a barrier layer.
U.S. Pat. No. 6,251,528b1 (Uzoh) shows a method shows a method for a Cu stud that involves a barrier layer.
U.S. Pat. No. 6,362,027(Yamazaki et al.) shows an interconnect with a Ta layer.
FACTORS CONTROLLING THE STRUCTURE OF SPUTTERED TA FILMS, by G. Feinstein and R. D. Huttermann, Thin Solid films, Vol. 16, pages 129-145 (1973) shows beta phase Ta processes.